Can't change air flow direction on ac/heater control. Only blows up to windshield.

What have you checked so far ?
Radiator full of coolant ? Heater hoses getting hot ?

. Air won't blow out of the floor or center vents just defrost ? Do you have manual or automatic climate control ?
Air Flow Control
Air flow control is accomplished in the following manner:

• Primary control is through the function selector knob mounted on the A/C-heater function selector switch, which is part of the integrated control panel.
• The function selector knob has the following positions: OFF, MAX A/C, A/C, PANEL, PANEL/FLOOR, FLOOR, FLOOR/DEFROST and DEFROST. The A/C-heater function selector switch combines a vacuum selector valve with an internal electrical switch.
• The vacuum selector valve directs source vacuum to various vacuum control motors (18A318). Refer to the Vacuum Control Diagram , System Airflow Schematics and Vacuum Control Chart .
• Two internal, single-pole electrical switches are also controlled by the A/C-heater function selector switch. The combination of these electrical switches controls the electrical supply to the A/C clutch and heater blower motor switch (18578).
• The position of the function selector knob determines the manner in which the system will operate.
• Each position of the function selector knob is detented for positive engagement.
• Vacuum Control Motors The vacuum control motors (18A318):
  
  • are located on the A/C evaporator housing, A/C recirculation air duct and heater air plenum chamber (18471).
  • direct system airflow to the vehicle interior as determined by the remote climate control module or manual override.
  • The five-passenger seating configuration has an additional vacuum control motor mounted on the heater air plenum chamber to control airflow to the rear seat A/C register (19893).
  
  

There is no vacuum to the controls. Look for a vacuum hose that is no longer connected to the engine intake manifold and repair it.

HEATER AIR DAMPER DOOR STUCK OR FAULTY HEATER AIR DAMPER DOOR MOTOR.

feel the two hoses going into and out of the heater core. they both should be hot. if one is cold the heater core is likely plugged. you can try flushing it out to see if you can restore flow to the heater core. if they are both hot the thermostat may be sticking open tho you should have a limited amount of heat. also confirm that the vents are operating as they should be.

robert

most likley you have a vaccume leak somewhere but also the linkage to the door that that directs the air flow may be in a bind. another possability is the hvac controlls. hope this helps

Your problem is the air temp control blend door actuator is defective and not controlling temp u set. to change/access this part the dash assembly must be removed from the car.

If you have the heater directed to the windshield, the AC will turn on. Move the control away from defrost.

there is a valve on one of the heater hoses that is run by vacuum if it don't work hot water will not enter the heater core. If it does work maybe the heater core is just plugged up.A quick fix for that is swapping the heater hose's I know one is bigger than the other but if you can it will change flow direction and it will flush the core. It should work after that. Heaters aren't controlled by the cars computer they may be controlled by the controller but thats cars with climate control

headlights won't turn off.. 1998 fors tuarus